Thermal Numerical Simulation and Correlation for a Power Package

Thermal resistance is sensitive to package structure, package material, thermal test board and ambient conditions. In this paper, a power package (D2PAK), with natural convection is studied. For the thermal test board, the special designed boards called "MINI Pad" board and "One Square Inch" board for power application are employed based on actual thermal testing. A testing procedure of thermal resistance theta JA for TO serial power products is introduced. Several factors in this procedure, such as the connection wires, socket and interface board are studied and discussed in order to reduce the heat loss by the connection fixtures which are not involved in FEA models. In the simulations, constant empirical heat transfer convection coefficient and temperature-dependent of it are applied on the FEA models separately as boundary conditions, and then the correlation from the simulation results to the measurements is examined. It is found that temperature-dependent formula of heat transfer coefficient is more reasonable for thermal simulation.